Field Of The Invention
The invention relates to a method for checking the operating reliability of a turbine during load shedding with a regulating circuit for regulating the rotational speed of the turbine. The invention also relates to a corresponding apparatus.
A regulating device for turbines with rotational speed regulation and power regulation is disclosed in Published, Non-Prosecuted German Patent Application DE 26 27 591 A1. In order to prevent an emergency shutdown protection device from responding due to excessively high over-speeds in the event of sudden load cutoffs, it is specified therein that the speed regulator and power regulator are configured to be functionally independent of one another over the entire working range, the correcting variables of these two regulators being fed as input signals to a minimum element.
A power monitoring system for gas turbines is disclosed in British Patent Application GB 2,011,126 A. A regulating network regulates the rotational speed of the gas turbine. Detection devices, by which a load change is detected, are provided. The detection devices generate a signal which represents the load change and modifies the output signal from the regulating network in such a way that delays caused by the regulating circuit are eliminated or reduced.
Published, Non-Prosecuted German Patent Application DE 14 01 456 A is concerned with a device for regulating the rotational speed of turbines. A multi-loop regulating circuit is provided, which contains an electric rotational speed regulating part-circuit and an electrohydraulic regulating part-circuit which is subordinate to the latter and which determines the opening of the actuating members releasing the supply of energy. The properties of a hydraulic component which are disadvantageous for regulating dynamics, such as inertia or nonlinear amplification, are compensated by such a regulating circuit.
A regulating device for regulating the rotational speed of a turbine and a method for regulating the rotational speed of a turbine during load shedding is disclosed in German Patent DE 19 528 601 C2. A first regulating structure with a PI controller, to which a deviation signal can be supplied, is provided. The deviation signal is dependent specifically on the difference between the desired value and actual value of the rotational speed. The first regulating structure is connected to an actuator serving for regulating the rotational speed. The first regulating structure serves for regulating the rotational speed when the turbine is in the no-load and/or isolated operating mode. During load shedding, a closing signal is fed to the actuator. The proportionality constant of the PI controller is selected in such a way that, where a deviation signal of a predeterminable minimum size is present, the output signal from the PI controller assumes the value 0. Such a regulating device affords a uniform and simple possibility for regulating the rotational speed of the turbine, without the need for additional load jump equipment that is intended to prevent an emergency shutdown of the turbine in the event of load shedding.